414 FIFTH REPORT OF THE ENTOMOLOGICAL COMMISSION. 
with the words: " I <lo not feel fully prepared to agree with Mr. Riley and Miss 
Smith in regarding all tin- J'lilciiKirin- found on these plants as identical, but there is 
enough evidence t" show that this insect is capahle of thriving on quite a variety of 
food-plants, and in the cases where it ha^ been directly introduced from the maple 
there is no question of its identity." We have also found what is evidently the same 
Bpeeiea doing considerable damage to the woodhine {Ampelopnis veitehii) on our resi- 
denoe at Washington. 
Mode of spreading. — Owing to the wingless, degraded, and inactive character of the 
female and the limited capabilities of the young for extended locomotion, the problem 
as to how the insect spreads from one locality to another seems at first glance rather 
a difficult one. When we consider the great activity of the young lice, however, 
and their propensity for fearlessly crawling upon anything which happens to be in 
their immediate vicinity, the difficulty is lost sight of. We may recognize as aids in 
transportation (1) the transplanting of trees from infested localities to places free 
from this insect, (2) birds, (3) other insects, (4) winds, and (5) water. The first of 
these methods needs no comment. The second is undoubtedly one of considerable 
importance, though scarcely deserving the prominence given it by some writers. Mr. 
Walsh, in his first report as State Entomologist of Illinois (p. 41), in speaking of the 
oyster-shell bark-louse of the apple (Mytilaspis pomorum), made the following state- 
ment : 
" In my opinion the only way in which, as a general rule, bark-lice can spread 
from tree to tree, when the boughs of those trees do not interlock, is by a few of 
the very young larva), when they are first hatched and are scattered over the limbs of 
a tree in such prodigious numbers, crawling accidentally onto the legs of some bird 
that chances to light upon that tree and afterwards flies off to another. I have long 
observed that when a tree first begins to be attacked by bark-lice, it is only particu- 
lar limbs and branches that are at first infected, and that these will be swarming 
while the rest of the tree will be free from lice. And I have further observed that 
it is the lower horizontal limbs, or branches, or such as birds, with the exception 
of woodpeckers and nut-hatches, would most naturally perch on, that are first 
attacked. * * * If all the birds in the world were killed off, I believe that these 
bark-lice in a very few years would cease to exist." 
This is an extreme view, and we have already shown (First Missouri Ent. Report, 
p. 15) how little the agency of birds is to be compared with that of insects. In the 
case of the species under consideration, the copious secretion of honey-dew attracts 
many honey-loving insects, such as bees, wasps, and flies, and these without doubt carry 
many of the restless young larvae from tree to tree. Even the natural enemies of the 
bark-lice assist in this transportation, and Mr. Hubbard states (American Naturalist, 
May, 1882, vol. xvi, p. 412) that the Coccinellid beetles Hyperaspidius coccidivorus, 
Chilocoru8 bivulnerw, and others, while feeding upon the young larva? of orange scale- 
insects, carry many of them from one tree to another attached to their backs and 
legs. 
Mr. Hubbard has more recently come to the conclusion that spiders are very im- 
portant agents in the distribution of scale-insects, in fact, the most important of all 
agents, and as his remarks apply quite well to the insect and the topic under consid- 
eration, we quote from a letter published in Bulletin No. 2 of this Division, pp. 
30-31 : 
11 1 have reached the conclusion that spiders play a much more important role in 
'assisting the spread of scale-insects than any other insects. From the beginning of 
my observations I have noticed that leaves which spiders had folded or webbed 
together for their nests or lairs almost always proved infested with scale, if infested 
trees were found in the neighborhood. This I was at first inclined to attribute solely 
to the protection from enemies and parasites afforded by the web and presence of the 
spider. No doubt, where the source of infection is near at hand, this may give a 
sufficient explanation of the observed facts. Lately, however, I have been examin- 
